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Need some help with fetch requests
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Need some help with fetch requests


  • Subject: Need some help with fetch requests
  • From: "Carter R. Harrison" <email@hidden>
  • Date: Fri, 1 Feb 2008 15:03:32 -0500

Hi All,

Today I'm working with NSFetchRequests for the first time and I need some help learning how to filter down the initial set of managed objects that I want to search against. My application is a sort of message viewer/editor. A user can open up multiple files, each containing some number of messages. Messages themselves are broken down into any number of fields. So my managed object model follows that same type of hierarchy..

Entity: File
Relationship: Messages

Entity: Message
Relationship: Fields

Entity: Field
Property: Value (string)

When a user performs a search, the search will be performed on the "Field" entity's "Value" property. I can make this work great with an NSFetchRequest. My issue is that the search is searching all Field objects, even if they are owned by a different file. I want to be able to search just the fields in the currently selected file, rather than all files that are currently open in the application. Hope that makes sense. My initial thought was to add more criteria to my predicate to help narrow down the search base, but I'm not sure how the predicate's criteria could traverse relationships. Thanks in advance for the assistance.

Regards,
Carter
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